1. Field of the Invention
The present invention relates to high quality cylindrical locks provided with an intruder or security classroom function in which the lock mechanism can be locked with a key from the inside to prevent entry by an intruder into an occupied classroom or office. The invention is particularly useful in lever handle designs, often required in public buildings, where an intruder could apply a very high level of torque to the locking mechanism through the lever handle.
2. Description of Related Art
Locks used in commercial and public buildings, such as office buildings and schools, are increasingly being provided with a security classroom function (also referred to as an “intruder” function). This type of lock is typically used on inner doors to separate classrooms or offices from hallways or public areas.
Locks with this function have key operated lock cylinders on both sides of the door. Turning the key on either side of the door will lock the door and prevent the outer handle from opening the door. Regardless of whether the door is locked or unlocked, however, the inner handle always retracts the latch and opens the door to allow those inside to exit, if necessary. A principal advantage of this lock function is that the door can be locked from the inside without opening the door and without exposing those inside to an intruder who may be located on the other side of the door.
As compared to more conventional lock designs with a button lock actuator on the inner side of the door, locks with this function provide a more positive control of the locked state of the door. Those without a key for one of the two lock cylinders cannot change the locked state of the door. This reduces nuisance locking as may occur with a conventional button lock actuator, which does not require a key to lock the outer door from the inside.
Different keys may be used for the inside and outside lock cylinders in a lock equipped with this function. This allows teachers or office workers to be issued an inside key to activate the intruder function from the inside, but does not allow them to have access to that room (or any other locked room) from the outside, if it is locked.
Locks that are currently available with this function have typically been designed with a single locking mechanism that is actuated by either of the two lock cylinders to switch the locking mechanism to or from the locked condition. If the door is placed in the locked condition from the outside lock cylinder, it can be reverted to the unlocked condition from the inside cylinder and vice-a-versa.
One problem with this type of conventional design is that the door may be switched to the unlocked condition with the outside key without the knowledge of those inside. As a result, those inside cannot always be certain as to the locked state of the door, even after it has been locked from the inside and even though the door has never been opened. The door may have been unlocked inadvertently from the outside by authorized security personnel or by police with an outside key when attempting to lock the door or when checking to ensure that those inside are safe or that the intruder is not located within.
A related problem with existing locks having this function is that opening the door from the outside with an outside key will typically unlock the door automatically. When police or security personnel open the room, they must remember to insert the key and lock it again. In the confusion surrounding an intruder event, where police or security personnel may not be familiar with correct operation of the lock, rooms that are securely locked before entry may become unlocked.
The strength of the lock is a particular concern when applied to a lever handle design. Doors are much easier to open when the door handle is shaped as a lever handle rather than a conventional round knob. For this reason, lever handles are preferred in some applications, and they may be required under applicable regulations for certain doors in public buildings to facilitate access by the disabled and the elderly.
However, the lever shape of the door handle allows much greater force to be applied to the internal locking mechanism of the door than can be applied with a round knob. In most door locks, the lock mechanism prevents the knob from being turned when the door is locked. When a round door knob is replaced by a lever handle, the greater leverage available from a lever handle may allow an intruder to break the internal components of the lock mechanism by standing or jumping on the lever end of the handle. This problem is particularly acute for cylindrical locks, which have less internal room than mortise type locks to accommodate heavy-duty locking components.
Another problem relates to the unbalanced shape of a lever handle, which tends to cause the lever handle to droop. A conventional round doorknob is balanced around the rotational axis of the handle. Thus, it takes relatively little force to return the handle to the rest position. This return force is usually provided by the latch rod return springs in the lock. A lever handle, however, requires much more force to return it to the level position. Sufficient force cannot be provided by the latch rod return springs, so most lever handle designs incorporate auxiliary lever handle return springs.
Because the lever handle return springs are large, and because there is limited space inside the lock, the auxiliary lever handle support springs have heretofore been located in the rose. While this is effective, locating the lever handle return springs in the rose produces a thick rose that is considered by some to be relatively unattractive.
The visual symmetry of a round doorknob means that it is not critical that the knob return exactly to the rest position when the handle is released. However, if a lever handle does not fully return to the level rest position, it appears to droop. Such visual droop is particularly objectionable. A rest position that is slightly above level, however, is generally not considered to be objectionable.
To avoid visual droop, as a result of normal wear or component tolerances, it would be desirable for the rest position of the lever handle to be slightly above horizontal. However, heretofore it has been difficult to arrange for the lever handle to return to a position above level without constructing the lock in two different versions for left-hand swing and right-hand swing doors or without placing the stops in the rose.
A conventional lock can be installed in either a left-hand swing or a right-hand swing door by flipping the lock top for bottom. This keeps the locking side of the lock mechanism on the same side of the door, while allowing for both the left-hand swing and right-hand swing operation. If the stop position were to be located in the lock mechanism, however, this rotation about a horizontal axis would cause the above-level stop position to reverse to an objectionable below-level position. Requiring separate locks for left and right-hand swing doors, however, is undesirable as it increases inventory costs and results in confusion and delay when the wrong lock is ordered.
Accordingly, the stops are usually placed in the rose. This allows the rose to be reversed relative to the lock body, as needed to always keep the top of the rose at the top regardless of whether the lock is installed in a left-hand or right-hand swing door. Placing the stops in the rose, however, is undesirable, as it requires that the rose be made thick to accommodate the stops.
When the rose is used to provide the stops to limit handle motion and to house the return springs, is necessary to anchor the rose relative to the door. Usually this is done with through-bolts, which connect roses on opposite sides of the door and pass outside of the main hole for the lock body. Through-holes, however, require a large diameter rose to cover these holes. Such a large diameter rose is considered by some to be unattractive and the large diameter increases the cost of the rose.
Another problem with prior art lever handle cylindrical locks arises as a result of the method used to attach the handle to the lock mechanism. Generally, the handle slides over a shaft and is captured by a spring loaded capture piece. The capture piece must have some clearance from the hole that captures it, and this clearance allows axial motion between the shaft and the handle. This motion is perceived as a “loose” handle by the user and is undesirable. Often, there is also some relative motion between the shaft and the lock mechanism as well, which contributes additional objectionable axial motion between the handle and the door. It is highly desirable to reduce or eliminate this axial endplay between the handle and the lock mechanism.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a lock mechanism having a security classroom function wherein the inner lock cylinder and the outer lock cylinder operate independently to keep the outer handle locked such that the outer lock cylinder can be used to open the door when the inner lock cylinder is in the locked state, but the outer lock cylinder cannot permanently unlock the outer handle for entry from the outside unless the inner lock cylinder is also changed to the unlocked state.
A further object of the present invention is to provide a lock mechanism for use with lever handles that is strong and resistant to abuse.
It is another object of the present invention to provide a lock mechanism for use with lever handles that does not require boring through-holes.
A further object of the invention is to provide a lock mechanism for use with lever handles that uses thin and small diameter rose plates.
It is yet another object of the present invention to provide a lock mechanism for use with lever handles that has reduced endplay between the handle and the lock body.
It is still another object of the present invention to provide a lock mechanism for use with lever handles that can be more completely disassembled and repaired in the field.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.